Best Western Rewards - Can't book property through BW.com - what is the "restricted list"?

I'm considering booking a room at a BW property (in Debrecen, Hungary, to be precise). It is listed on hotels.com. If searching on BW.com, it does not come up by location - only when I search by name ("Hotel Kalvin"). But unlike hotels.com, which shows full availability, it is not shown as available - not on my preferred date, not during the entire month, not ever. I just phoned BW and all they could tell me was that this property was on the "restricted list", meaning that they could not take bookings either online or over the phone. They refused to comment as to whether or not this could mean that there was a problem with the property and/or its status within the BW chain. Does anybody know anything about this restricted list and what it means? Sounds absolutely bizarre both from the point of view of the chain and the actual property.